#include <iostream>
#include <stdio.h>
using namespace std;
const int MAXN=3e5+7;
typedef long long ll;
ll ask[MAXN];
int res[MAXN];
int main() {
	int n;
	while (cin>>n) {
		for (int i=0; i<n; ++i) {
			cin>>ask[i];
		}
		res[0]=-1;
		for (int i=1; i<n; ++i) {
			if (a[i]-a[i-1]<=1000) {
				res[i]=1;
			}
			else if (a[i]-a[i-1]>=2000) {
				res[i]=-1;
			}
			else {
				res[i]=0;
			}
		}
		if (res[n-1]==-1) {
			cout<<"Impossible"<<endl;
		}
		else {
			res[n-1]=1;
			for (int i=1; i<n; ++i) {
				
			}
		}
	}
	return 0;
}
